Seafood is an excellent food that is increasingly popular because of its low fat and low cholesterol content and other health benefits. Unfortunately, it is also subject to rapid spoilage and is not safe to eat if not eaten within a short time of harvesting, i.e., within a couple of days, or treated to high energy processes such as canning or freezing which generally change the texture and flavor of the seafood markedly.
Seafood spoilage is mainly due to the rapid growth of bacteria in fresh seafood, particularly bacteria such as the psychotropic type, including Pseudomonas and Achromobacter. These bacteria grow rapidly, e.g. to a level of 10.sup.6, within a few days. They also produce hydrogen sulfide, which adds a noxious odor to the seafood.
Thus various researchers have attempted to find ways of preserving fresh seafood to prolong its shelf life to up to a week or more without causing a deterioration in the texture or flavor, and while maintaining safe levels of bacteria
Chemical techniques for preserving seafood have been studied. For example, dipping fish in potassium sorbate successfully inhibited the growth of bacteria in English sole.
At a 1% concentration, microbial growth was inhibited for up to six days. However, this method is concentration dependent; little inhibition was noted at 0.1% sorbate concentration, and little or no inhibition was noted for this treatment for other species of fish such as red hake and salmon.
Chemical preservation combined with packaging under a modified atmosphere has met with some success in decreasing the bacterial spoilage of fresh seafood In one study, Australian morwong fish exhibited extended shelf life when dipped in 1.2% of potassium sorbate and 10% polyphosphate, followed by packaging in 100% of carbon dioxide. However, maintaining fish in an atmosphere other than air greatly increases the cost of the product. Rock fish fillets dipped in 1% potassium sorbate and 5 ppm of chlorotetracycline, followed by vacuum packaging and storage at 2.degree. C., greatly extended their shelf life up to 14 days. However, again this method is expensive and burdensome for both fish suppliers and handlers.
Thus a method of extending the shelf life of fresh seafood by inhibiting the growth of odor and spoilage-causing bacteria and improving the texture of the seafood in a non-energy intensive manner, has long been sought.